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1 - Introduction

With Weather Defender you can track Hurricanes, Tropical Storms, and other cyclonic activity. Different from other Weather Layers, a set of Hurricane Layers is provided for every active storm, and continuously updated. Seventeen layers in all give you extremely detailed and precise information about each Hurricane's track and anticipated movements.

Hurricane Tracking Layers

1.1 - Access

Hurricane Layers are available from the Layer Browser during Hurricane Season each year (generally June through December).

You may be required to upgrade your account before accessing the Hurricane Layers.

1.3 - Update Frequency

The Hurricane Centers have the following standard times for forecast advisory issuance:

09 UTC (5 AM EDT) Where UTC is also known as GMT or Zulu

15 UTC (11 AM EDT)

21 UTC (5 PM EDT)

03 UTC (11 PM EDT)

As with other Weather Layers in Weather Defender, Hurricane Layers will automatically update when added to your Map.

2 - Layer Descriptions

2.1 - Hurricane Summary

The Hurricane Summary layer is a compilation of all active tropical weather systems. It will display all storm locations and forecasted tracks on a single map. Tooltip (mouse-over) information provides: storm name, category, max winds, and latest advisory number & time. Clicking on the hurricane icon will display the most recent advisory text.

2.2 - Current Winds

The Current Winds layer will display up to three rings, representing the extent of tropical storm force winds (34kt or 39mph) in blue, 50kt or 58mph winds in yellow, and hurricane force (64kt or 74mph) winds in red. These are the 3 standard wind ranges provided by the Hurricane Centers.

2.3 - Forecast Points, Forecast Line

The Hurricane Center issues storm location and intensity projections for up to seven time periods: 12, 24, 36, 48, 72, 96, and 120 hours into the future. Forecast Points are shown as open squares along the forecasted track. They are labeled by default with the date and Eastern Time.

Forecast Line is the dashed line ahead of the storm representing where the storm center is projected to track within the next 3 to 5 days (72 to 120 hours).

2.4 - Forecast Winds

Forecast Winds represents a composite of wind ranges throughout a 72-hour forecast period. The fill colors represent the extent of tropical storm force winds (34kt or 39mph) in blue, 50kt or 58mph winds in yellow, and hurricane force (64kt or 74mph) winds in red.

2.5 - Error Swath

The large white swath in the middle represents the area in which the storm center is most likely track within the next 72 hours (3 days). The swath gets wider at a rate equal to the average error rate per hour of forecast, and thus is quite wide in the latter hours. This reflects the uncertainty in the hurricane forecast process, specifically the 10-year average forecast track error. The swath means that even though the Hurricane Center has forecast a specific track, the storm could end up anywhere within the swath within the next 72 hours, with around a 60% confidence level.

Tropical storm force winds might occur in the hatched area if the storm tracked at the outer edge of the error swath.

The transparent gray area beyond the white swath represents the Average Error Swath for 73 to 120 hours (5 days).

2.6 - Wind Probabilities: 39, 58, 74 MPH

Probabilities for winds of at least 34kt, 50kt, and 64kt are derived from three separate layers: Probs 39 MPH, Probs 58 MPH, and Probs 74 MPH.

Wind probability layers contain polygons representing 5 ranges: probabilities of at least 5%, 10%, 20%, 30%, and 50%. These polygons are the result of boundary analysis performed on the TPC/NHC's gridded wind probability products.

2.7 - Past Points, Past Line

Past Points are the observed locations of the storm center at the time of previous advisory issuances. They are colored according to the maximum intensity of winds at those times: White (<39 mph), Blue (>39 mph), Yellow (>58 mph), Red (>74 mph).

Past Line is the solid line representing the actual path the storm has taken.

2.8 - Past Winds

The fill colors represent the extent of tropical storm force winds (34kt or 39mph) in blue, 50kt or 58mph winds in yellow, and hurricane force (64kt or 74mph) winds in red.

2.9 - Watches Warnings

Watches and warnings appear as lines along the coast and as points marking the starting and ending location for each item.

Hurricane warnings (red) are issued when hurricane conditions are expected within 24 hours and hurricane watches (pink) are issued when hurricane conditions are possible within 36 hours. Tropical storm warnings (blue) are issued where those conditions are expected within 24 hours and tropical storm watches (green) are issued when that threat is possible within 36 hours.

2.10 - Rainfall Estimates: 24, 48, 72 hours

The Rainfall layers are derived from the HPC (NOAA Hydro-Met Prediction Center), which issues 24-hour rainfall forecasts for Day 1, Day 2, and Day 3. The polygons are isopleths of rainfall amount, meaning that higher amounts of rain are nested within the lower amounts.

Polygons are color-shaded based on the expected rainfall amount: light green for less than 1 inch, medium green for 1-4 inches, and dark green for more than 4 inches.

2.11 - Flood Outlook

The Flood Outlook is also derived from the HPC which issues a 5-day forecast of freshwater flooding hazards for the continental United States, using more specific forecasts for each flood basin provided by several regional NWS River Forecast Centers around the country.

The forecast takes the form of polygon regions that are outlined in colors according to the likelihood of flooding. The categories are defined as follows:

Occurring/Imminent (red) - Significant flooding is already occurring or is forecast to occur during the outlook period.

Likely (blue) – Significant flooding can be expected during the outlook period.